Tenn. lab discovers method to remove carbon from air

Using X-ray diffraction, Oak Ridge National Laboratory's Radu Custelcean analyzed the molecular structure of the guanidine compound and was surprised to find carbonate, a crystal that forms when carbon dioxide from air reacts with water.(Photo: Provided by Genevieve Martin, Oak Ridge National Laboratory via Knoxville (Tenn.) News Sentinel)

KNOXVILLE — Researchers from a laboratory in Tennessee have discovered a new method for removing carbon dioxide from ambient air while conducting a study that was intended to help remove contaminants from water.

According to a news release by Oak Ridge National Laboratory, the new method is simple and reliable. The discovery is being billed as a new option to capture and store carbon and help combat global warming.

Scientists at the lab in Oak Ridge, Tenn., discovered the new method while trying to use a compound called guanidine to remove contaminants such as sulfate, chromate and phosphate from water. Radu Custelcean, a research scientist at the lab, said in a release that after exposing a solution containing the guanidine to air, researchers found crystals forming in the solution.

“After analyzing their structure by X-ray diffraction, we were surprised to find the crystals contained carbonate, which forms when carbon dioxide from air reacts with water,” said Custelcean.

The new crystallization method differs from other carbon-capture methods in that it requires considerably less energy to release the carbon from the guanidine solution and transfer it into long-term storage and transportation pipelines.

“Through our process, we were able to release the bound carbon dioxide by heating the crystals at 80-120 degrees Celsius (176-248 degrees Fahrenheit), which is relatively mild when compared with current methods,” Custelcean said.

The crystallization method compares favorably to traditional methods which require carbon capturing materials be heated to 900 degrees Celsius, or 1,652 degrees Fahrenheit, before the captured carbon can be released for transportation and storage. The lab's new guanidine-based method requires much less energy and allows the guanidine solution to be re-used as many as three times.

Custelcean added by phone that it would take a concerted government initiative for the new method to become a widespread practice.

Charles Seipp, of Oak Ridge National Laboratory, synthesized a simple compound known as guanidine that was found to bind strongly with carbon dioxide directly from the air and form insoluble carbonate crystals that are easily separated from water.(Photo: Provided by Genevieve Martin, Oak Ridge National Laboratory via Knoxville (Tenn.) News Sentinel)

“It really all depends on the policies and regulations because there would have to be a nationwide initiative and that requires funding,” he said. “It would have to be initiated by the government.”

The new method’s potential to remove carbon from the air is strong Custelcean said, but he emphasized that the air is a shared resource and that removing and storing a large amount of carbon would take global cooperation.

“It would require a global effort,” he added. “If only one country were to tackle it, I think the magnitude would be too large.”

The crystals that were found in the guanidine solution are now being studied at Oak Ridge National Laboratory's Spallation Neutron Source in the hopes of better understanding the mechanism behind guanidine’s ability to absorb and release carbon dioxide.

The study detailing the experiment, titled “CO2 Capture from Ambient Air by Crystallization with a Guanidine Sorbent,” was published in the journal Angewandte Chemie International Edition and included Charles Seipp of the University of Texas at Austin, Neil Williams of the University of Tennessee, Michelle Kidder and Custelcean, all of whom also work for Oak Ridge National Laboratory.

Funding for the project was provided by the Department of Energy’s Office of Science.